Power System Reliability Report - RTE

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R-AUDIT-SG-DAR-MAS-11-2011/022010 Reliability ReportPage : 32/408 juillet 2011Finally, 1110 ESS level 0 were declared (-10% compared with 2009). It is important to record theseincidents, even if they only moderately affect reliability 23 , because the information is valuable toimprove feedback and to carry out theme analyses. The analysis of these events is also instructivebecause some of these incidents could, in other conditions, be an elements setting off a seriousreliability incident.In 2010, the CNREX therefore examined several ESS level 0 concerning the uncontrolled loss of twotelecommunications links, one of which is needed for rapid clearing of short circuits on the "close"225 kV or 400 kV links 24 , for a duration of a few hours to a month. These problems are mostly linkedto a lack of rigour and communication between the multiple participants concerned by unavailabilitymanagement (unscheduled or scheduled), sometimes lasting a long time, that can affect one and thenboth of the remote transmission links required for the associated protections (line differential and/orstage acceleration for distance protections). In addition to the decided improvement actions, whichare partly linked to the recommendations of the flash audit mentioned above, these malfunctions,potentially serious for reliability, require long term vigilance by regional management.The evolution of ESS level 0 also highlights the growing trend of non-operability of the 400kVstructures‟ busbar switch disconnectors, detected during operating manoeuvres or periodic operationscarried out for preventive maintenance (OMF). The incomplete operation of this equipment can have aserious impact on electrical system reliability with the risk of double busbar fault if the fault occurswhen a busbar change for a given equipment is performed (as happened on December 21 st 2009 atTavel). Moreover, operating restrictions that may be imposed before repairs following the observationof a fault reduce the possibilities of action in the concerned substation when there is an operatingproblem to deal with. Different actions are being pursued to control these faults, in the short and longterm: a replacement and securing programme in the South-East, development of corrective actions fora category of equipment, study of a future renewal programme. The critical nature of this equipmentfor reliability requires sustained, long term action and the process followed must be complete.Among the production-related ESS level 0, the graph below presents the number logged since 2001for generating unit control withdrawals of more than 2hrs in secondary voltage control (RST-N andRSCT), in secondary frequency-power control(RSFP) and in primary frequency control. It showsan upward trend in unit control losses in secondaryvoltage control, already indicated in last year‟sreport. These withdrawals of control should beconnected to the increase in reactive powercapacity limitations; they result in difficulties forsystem control to efficiently manage variations ofthe voltage profile inherent to injection,consumption and flow variations, or unit trippings.Since 2010, events affecting the European interconnected network on the Central-West Europe zonehave been logged by the German, Belgian, Dutch, Luxembourg, Swiss and French TSOs according to acommon classification grid, similar to RTE‟s. The number of logged incidents has gone downsignificantly: 264 level 0, 18 level A, 8 level B, compared to 418 level 0, 46 level A, 19 level B, 1 levelC, 2 level D in 2009.The published report indicates that two incidents of non-compliance with the 400 kV N-1 rule werelogged (including the one on April 20 th in the eastern France), for short durations and without anypotential impact for the neighbouring TSOs. This result may be considered to be satisfactory, on thecondition that these situations are correctly identified by all the TSOs. The report highlights that thisimportant point should be related to progress in the development of operational cooperation betweenthe TSOs concerned, based on different ad-hoc structures, such as CORESO, favouring riskidentification and the implementation of concerted solutions (as already noted for CORESO, §2.4). In23 Hence, we declare as an ESS level 0 for any untimely tripping of a generating unit and any tripping of a400 kV line, although these contingencies are covered by the application of the N-k operating rule.24In the 3 cases, this concerns lines whose short-circuit elimination times must be short enough to guarantee thedynamic stability of high capacity units.Copyright RTE. This document is the property of RTE. Any communication, reproduction, publication even partial is forbidden without the express written authorisationElectricity Transmission System operator (RTE)
R-AUDIT-SG-DAR-MAS-11-2011/022010 Reliability ReportPage : 33/408 juillet 2011addition, amongst the level A and higher incidents, and if we set aside high voltage overruns on the400 kV network declared mainly by Elia, which hardly affect system reliability, the potentially worryingevents are: two losses of the main power-frequency regulator by a TSO and 11 non-concomitantlosses of observability of the 400 kV network by different TSOs, for levels (scope and duration) moreor less serious.6.2 Feedback other than ESSRTE teams perform reliability-related feedback analyses that are not limited to ESS occurrences, on aregional as well as a national level, particularly in the context of the CNREX and the TransmissionTechnical Committee. Different annual technical reports – telecontrol, line and substation equipment,and protections – are drawn up and examined by these committees to monitor underlying evolutions.Thus, following the infection of different industrial systems worldwide by the "Stuxnett" virus, ananalysis looking at the vulnerability of RTE‟s digital instrumentation and control methods was carriedout. The CNREX approved the conclusions reached: though this virus did not infect the equipment,other relatively harmless viruses were found in different installations, but the regions were notaffected; the measures set up therefore seem to protect the equipment properly if they are strictlyapplied. They were strengthened nevertheless and regular awareness raising actions are required.The CNREX also examined the learnings from the flood on 15 th June in the Var. Confronted with awater level much higher that the 100-year flood level, the 225 and 63 kV Trans substations werebadly damaged, but the recent 400 kV substation was not harmed, in accordance with therequirements established for construction 25 . The preparations for the event announced by the weatherforecast meant that the right decisions could be made, in particular for load shedding conditions toavoid the propagation of the incident to a wider electrical zone than the one affected. The efficiencywith which the crisis was managed should be highlighted. In terms of corrective actions, apart fromthe upgrading of the damaged substations with a higher level of protection, preventive actions in caseof future flooding on a regional level have been undertaken: updated inventory of the vulnerability ofthe region‟s substations, analysis of the possibilities of "bridging" the 400 kV links, so as to be able tobypass flooded substations and thus reduce the risk of spreading the incident to the whole regionalnetwork.For all the 380 lines at 400 kV, the rate of unscheduled outage was 0.06 % (0.08 % in 2009) and therate of scheduled outage for work was 2.16 % (1.97 %). Amongst the 400 kV lines, there are 181“sensitive” ones in these 400 kV facilities, whose unscheduled absence in real time leads to significantproblems for the electrical system and for which RTE implemented specific measures (improvedmaintenance sets, quick-reaction equipment inspections even out of working hours in the event of atrip, etc.); their unscheduled outage rate stood at 0.04 %. Also to be noted are 67 "strategic" 400 kVlinks whose absence in operation causes inconvenience such that measures are required to reduce theneed to shut them off for maintenance purposes; the unscheduled unavailability rate was 1.47 %(1.67 %).These results are among the best annual ones for sensitive links and reasonable considering the lastten years for strategic links. They are clearly better than the results observed for the links overall,which is to be expected but has not always been the case. These results are by nature quite variableaccording to network incidents (small number of lightning strikes in 2010) and the type of work tocarry out for scheduled outages.Moreover, contractual commitments between RTE and the producer EDF regarding reliability aremonitored by a specific committee. The main themes examined were the methods of dealing with theunit reactive power limitations, the monitoring of actions taken on one side or the other following anincident, application of the contract on network restoration and voltage recovery.25 Within the scope of the Flood Risk Prevention PlanCopyright RTE. This document is the property of RTE. Any communication, reproduction, publication even partial is forbidden without the express written authorisationElectricity Transmission System operator (RTE)
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Power System Reliability Report - RTE

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